package main

import (
	"fmt"
	"sort"
	"strings"
	"time"

	"verstak/internal/core/activity"
	syncsvc "verstak/internal/core/sync"
)

// GetSuggestions analyzes today's activity and returns conservative suggestions.
func (a *App) GetSuggestions() ([]activity.Suggestion, error) {
	events, err := a.activity.ListTodayEvents()
	if err != nil || len(events) == 0 {
		return nil, err
	}

	type acc struct {
		title  string
		kind   string
		events []activity.Event
	}
	grouped := make(map[string]*acc)
	for _, e := range events {
		grp, ok := grouped[e.NodeID]
		if !ok {
			n, err := a.nodes.GetActive(e.NodeID)
			title := ""
			kind := ""
			if err == nil && n != nil {
				title = n.Title
				kind = n.Type
			}
			grp = &acc{title: title, kind: kind}
			grouped[e.NodeID] = grp
		}
		grp.events = append(grp.events, e)
	}

	var suggestions []activity.Suggestion
	for nodeID, grp := range grouped {
		if grp.title == "" {
			continue
		}
		hasEntries, err := a.worklog.HasTodayEntries(nodeID)
		if err != nil || hasEntries {
			continue
		}

		notes, files, actions, other := countByType(grp.events)
		summary := buildSuggestionSummary(notes, files, actions, other)
		if summary == "" {
			continue
		}

		spread := timeSpread(grp.events)
		bursts := countBursts(grp.events, 10)
		min := estimateMinutes(bursts, spread, len(grp.events))
		conf, reason := confidence(bursts, spread, len(grp.events))

		suggestions = append(suggestions, activity.Suggestion{
			NodeID:           nodeID,
			NodeTitle:        grp.title,
			Summary:          summary,
			SuggestedMin:     min,
			EventCount:       len(grp.events),
			NodeKind:         grp.kind,
			Confidence:       conf,
			ConfidenceReason: reason,
			TimeSpreadMin:    spread,
		})
	}

	sort.Slice(suggestions, func(i, j int) bool {
		return suggestions[i].EventCount > suggestions[j].EventCount
	})

	return suggestions, nil
}

// AcceptSuggestion creates a worklog entry from a suggestion (compatibility wrapper).
func (a *App) AcceptSuggestion(s activity.Suggestion) (*WorklogDTO, error) {
	return a.AcceptSuggestionWith(s, s.SuggestedMin, "")
}

// AcceptSuggestionWith creates a worklog entry with optional overrides.
func (a *App) AcceptSuggestionWith(s activity.Suggestion, minutes int, date string) (*WorklogDTO, error) {
	d := date
	if d == "" {
		d = time.Now().Format("2006-01-02")
	}
	entry, err := a.worklog.AddWithDate(s.NodeID, s.Summary, "", d, minutes, true, false)
	if err != nil {
		return nil, err
	}
	_ = a.sync.RecordOp(syncsvc.EntityWorklog, entry.ID, syncsvc.OpCreate, worklogPayload(entry))
	mins := 0
	if entry.Minutes != nil {
		mins = *entry.Minutes
	}
	return &WorklogDTO{
		ID:        entry.ID,
		NodeID:    entry.NodeID,
		Summary:   entry.Summary,
		Minutes:   mins,
		Date:      entry.Date,
		CreatedAt: entry.CreatedAt.Format("2006-01-02T15:04:05Z"),
	}, nil
}

// HideSuggestion marks a suggestion as hidden for the session.
// The frontend tracks visibility; this is a no-op on the backend.
func (a *App) HideSuggestion(_ activity.Suggestion) error {
	return nil
}

// --- event analysis ---

func countByType(events []activity.Event) (notes, files, actions, other int) {
	for _, e := range events {
		switch e.EventType {
		case activity.TypeNoteCreated, activity.TypeNoteUpdated, activity.TypeNoteDeleted:
			notes++
		case activity.TypeFileAdded, activity.TypeFileDeleted, activity.TypeFileRenamed,
			activity.TypeFileCopied, activity.TypeFileMoved,
			activity.TypeFolderAdded, activity.TypeFolderDeleted, activity.TypeFolderRenamed:
			files++
		case activity.TypeActionCreated, activity.TypeActionDone:
			actions++
		default:
			other++
		}
	}
	return
}

// timeSpread returns minutes between first and last event.
func timeSpread(events []activity.Event) int {
	if len(events) < 2 {
		return 0
	}
	minTime := events[0].CreatedAt
	maxTime := events[0].CreatedAt
	for _, e := range events {
		if e.CreatedAt < minTime {
			minTime = e.CreatedAt
		}
		if e.CreatedAt > maxTime {
			maxTime = e.CreatedAt
		}
	}
	t1, err1 := time.Parse(time.RFC3339, minTime)
	t2, err2 := time.Parse(time.RFC3339, maxTime)
	if err1 != nil || err2 != nil {
		return 0
	}
	diff := t2.Sub(t1)
	return int(diff.Minutes())
}

// countBursts groups events into bursts where consecutive events
// are within `windowMin` minutes of each other.
func countBursts(events []activity.Event, windowMin int) int {
	if len(events) == 0 {
		return 0
	}

	times := make([]time.Time, 0, len(events))
	for _, e := range events {
		t, err := time.Parse(time.RFC3339, e.CreatedAt)
		if err != nil {
			continue
		}
		times = append(times, t)
	}
	if len(times) == 0 {
		return 1
	}
	sort.Slice(times, func(i, j int) bool { return times[i].Before(times[j]) })

	bursts := 1
	last := times[0]
	for _, t := range times[1:] {
		if t.Sub(last) > time.Duration(windowMin)*time.Minute {
			bursts++
		}
		last = t
	}
	return bursts
}

// estimateMinutes conservatively estimates suggested minutes.
func estimateMinutes(bursts, spread, totalEvents int) int {
	if totalEvents <= 1 {
		return 5
	}
	switch {
	case spread >= 60 && bursts >= 3 && totalEvents >= 8:
		return 30
	case spread >= 30 && bursts >= 2 && totalEvents >= 5:
		return 20
	case spread >= 15 && bursts >= 2 && totalEvents >= 3:
		return 15
	case totalEvents >= 3:
		return 10
	default:
		return 5
	}
}

// confidence returns a label and reason string for the estimate.
func confidence(bursts, spread, totalEvents int) (string, string) {
	if spread >= 60 && totalEvents >= 10 {
		return activity.ConfidenceHigh, fmt.Sprintf("активность растянута на %d минут, %d всплесков", spread, bursts)
	}
	if spread >= 30 && totalEvents >= 5 && bursts >= 2 {
		return activity.ConfidenceMedium, fmt.Sprintf("несколько всплесков активности за %d минут", spread)
	}
	return activity.ConfidenceLow, fmt.Sprintf("%d событий за %d минут, %d всплесков", totalEvents, spread, bursts)
}

func buildSuggestionSummary(notes, files, actions, other int) string {
	var parts []string
	if notes > 0 {
		parts = append(parts, fmt.Sprintf("заметки (%d)", notes))
	}
	if files > 0 {
		parts = append(parts, fmt.Sprintf("файлы (%d)", files))
	}
	if actions > 0 {
		parts = append(parts, fmt.Sprintf("действия (%d)", actions))
	}
	if other > 0 {
		parts = append(parts, fmt.Sprintf("события (%d)", other))
	}
	return strings.Join(parts, ", ")
}